Jib arms and cranes are known in a great variation of sizes and uses. They thus remove objects from one place to another. In some cases the object at first is to be moved vertically upwards, i.e. to be released from a supporting location, being located at a level of some nature, whereupon, possibly, the jib arm or crane may rotate and carry the object to a new position, the object then having been brought to a location lying at another, higher or lower positioned level or at the same level as that implied by the initial position. A lot of technical solutions and devices exist, which solve such tasks of transferring an object, being provided more or less automatically or mechanically.
Generally, the trend of development in respect of providing more automized jib arms and cranes tends towards devices which at best are to be distinguished as robots.
Jib arms and cranes to a large extend are being developed to be employed at specific applications being specific in that the objects, which are to be moved, do exhibit individually specific sizes and shapes. Thus, there may be jib arms of fine-mechanic nature, and cranes which are capable of moving objects of sub-grams sizes, and jib arms working with high-precision tolerances, and cranes capable of moving objects exhibiting weights sized in tons.
Furthermore, jib arms and cranes to a large extend are developed to be used within specific surroundings within which objects are to be moved around. Thus, a simulating of a human arm or hand may be wanted within an industrial plant, in which the surroundings are hostile to man.
Thus, as unique jib arms and cranes to be employed in fully unique surroundings by way of example can be mentioned jib arms and cranes serving to unload a satellite from a space shuttle for being positioned within a geostationary orbit in space. Such a jib arm or crane requires a very special technical layout in spite of when loading the same load into the space shuttle within other surroundings, quite another type of jib arm or crane is employed, and a third type of jib arm or crane is going to be employed when moving the same satellite in the working space where it is assembled.
A more specific range for the present invention to be used is in relation to offshore installations in relation to windmills. Such offshore windmills are to be deployed on base supports carried on the sea bottom and include towers to be erected upon these base supports.
In part while deploying these constructions, and in part especially when carrying out maintenance, inspection or repair of an offshore windmill it is required to be able to unload from a vessel loads which include construction elements or measuring equipments or minor elements intended for the windmill itself.
According to their nature these loads are forwarded to the site by means of a vessel and in most cases the vessel is approached closely to the base support of the windmill. Though, in some situations the vessel is anchored to the base support of the windmill, and in other situations of security reasons such an anchoring is not possible. It is thus also to be noted, that, as most commonly, the weather and the sea waves make an anchoring impossible. Furthermore, much time will have to be spend for the carrying out of an anchoring.
It is well-known that loads on a vessel in case of offshore installations by the use of a so called Jack up, which either is positioned on the vessel itself or on another vessel with the sole purpose to provide a hoisting means in an offshore environment.
In most cases a platform on either the base support or on the windmill tower taken in total in the following is designated as the pillar. This platform can be a platform which in a radial direction extends from the pillar, or it can be a platform which by 360° surrounds the pillar.
In U.S. Pat. No. 1,023,438 a crane is disclosed which comprises more joints and is fitted to be placed on a pillar.
Although this disclosed crane is useful in case of it being stationary deployed, the disclosed crane is relatively complicated assembled and can not be assembled nor be taken apart without difficulty.